


What's Yours Will Be Mine

by ambersagen



Series: Dean/Cas/Lucifer Verse [2]
Category: Supernatural
Genre: Established Castiel/Dean Winchester, Human AU, Implied future polyamoury, M/M, Multi, Sam is Dean's half brother, Twincest, Twins Cas and Lucifer, implied daydream about sex between consenting minors, which twin is which trope
Language: English
Status: Completed
Published: 2016-05-29
Updated: 2016-05-29
Packaged: 2018-07-10 20:43:08
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 915
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7005658
Author URL: https://archiveofourown.org/users/ambersagen/pseuds/ambersagen
Summary: <blockquote class="userstuff">
              <p>the original prompt:<br/>Cas and Lucifer are twins and Dean can't tell them apart. </p><p>Prequel to What's Yours Is Mine</p>
            </blockquote>





	What's Yours Will Be Mine

**Author's Note:**

> Mary and John are divorced in this fic. Sam is Dean's half brother, and lives with Mary.

“Hey bro!”

Cas winced, turning to his twin with a frown. “Indoor voice, Lucifer. Please. We’re in school, not a zoo.”

Lucifer shrugged, his identical face showing none of the sourness that his brother was currently wearing. 

“I need a ride. You’re boyfriend still hanging around in that boat of his?”

Cas snorted. “Don’t let him hear you call it that or you’ll never get within breathing distance of his car again.”

“Ugh, whatever. Do you think he’ll give me a ride or not?”

“Of course,” Cas sighed, ignoring his brother, who jumped on him jovially as he headed out to find Dean. He was probably already at the impala waiting for Sam to get out of class.

As it turned out, Sam was already at the impala too. The brothers were sitting in the front seat, windows rolled down as they sat back and took a rare moment to chat about their lives.

Suddenly, and without a word, Lucifer grabbed Cas, covering his mouth and pulling him down into a crouch behind a banged up little subaru. 

“Well well. Big Winchester and the elusive baby brother are having a little heart to heart, are they? Now’s the perfect time to do a little snooping and see what we can learn about our precious golden boy, huh Cassy?”

Castiel glared at his twin, licking the palm silencing him in an attempt to free himself, but Lucifer held on. 

“Don’t be an ass. You know there are all sorts of personal things he won’t talk about with you for fear of making you worry. What better way to find out about his homelife than to eavesdrop on his family bonding time with his half brother?”

Lucy wiggled closer to the impala, careful to keep both of them out of sight behind the other cars in the lot. There was faint music coming from the big black vehicle, but the twins could easily make out the conversation now that they were practically under Dean’s nose.

“What’s it like dating someone who’s a twin?” Sam was asking, hand hanging out the window to feel the breeze.

“Eh,” Dean responded, voice causing Cas to jump a little in guilt, but Lucifer held him down. “It’s exactly what you imagine. I don’t like to brag or anything, but my boyfriend is totally amazing, and easy on the eyes times two. Although,” he paused, considering. “It’s a good thing Cas dresses like an accountant, otherwise I wouldn’t know left from right twin.”

This time Cas bit Lucifer’s hand, and his brother let him go with a scowl. But Cas had no intention of revealing their location, and simply elbowed his brother over so he could hear better.

“Are you really telling me you can’t tell the twins apart except by their clothing?” Cas could perfectly picture the face of contorted incredulity he was making at his brother. 

“Well yeah,” Dean said, waving dismissively. “I mean, they’re just so similar!”

"Dude no,” Sam replied, appalled. “What are you even talking about. Cas is, like, totally nice and cool and smart. Lucifer is….well. He’s a devil. He’s totally evil.”

Dean laughed. “Are you kidding me? Cas can be pretty mean if he hasn’t had any caffeine in him for a few hours, and I know for a fact that he actually set Anna on fire in lab last year because she kept answering questions out of turn when he had his hand raised.”

Sam stared at him.

“Only a little though,” Dean backtracked. “Just like, her sleeve. And you’re the one totally dismissing Lucifer as evil when I know you barely know him outside of that time he and Gabe pranked you in freshman year. He can be pretty nice if you know how to talk to him. Did you know he tutors in science and english for adults who are trying to get their GEDs? The guy has a soft spot, somewhere deep in there.”

“So you know all these secret personality quirks, but you can’t tell them apart.” The judgement was practically dripping from Sam’s voice.

“Well, yeah. They are identical twins,” Dean responded, as if it were obvious. 

“...Is he an idiot?” Lucifer whispered, after an awkward pause. Cas looked uncomfortable as he obviously wanted to defend his boyfriend but couldn’t come up with anything in the face of what they were hearing.

“Besides,” Dean continued, unaware of his hidden audience. “Does it even matter how well I can tell them apart? It’s not like I hate one of them or anything. They’re both great.”

Sam huffed and something heavy landed on the table, possibly his head. “Of course it matters. You’re dating one of them! What’s going to happen if you start making out with the wrong twin just because their laundry gets switched?”

There was a long silence as both twins listened intently at the door. Dean didn’t say anything, but after a few seconds there was another, louder thump, and Dean yelping in protest. 

“Dude, stop thinking about banging twins when I’m right here you jerk.”

Cas rolled his eyes and Lucy smirked. 

“He’s still in big trouble,” Cas grumbled as they scooted backwards toward the front of the lot. 

“For sure, but that doesn’t mean I’m not gonna say I told you so. Because I told you so. Dean Winchester wants to be the creamy center to a Novak ice cream sandwich.”

Cas slapped his brother up the back of the head, but didn’t disagree. 

 

**Author's Note:**

> Comments feed my writing.
> 
> Come say hello. I am a lonely person.  
> ambersagen.tumblr.com


End file.
